1. Field of the Invention
The invention concerns a missile homing device. A standard weapons system has a missile launch ramp, a target-tracking device and a missile homing device. The target-tracking device may be of the radar type or of the optronic type but, in all cases, it covers a narrow field.
A missile is fired from a ramp located at a certain distance from the target-tracking device. Moreover, the trajectory of the missile, when it starts off, is a relatively random one, even if the direction of the launch ramp is perfectly parallel to the line of sight of the tracking device towards the target. Consequently, there is little chance that the missile will enter the narrow field covered by the target-tracking device. It is therefore necessary to provide for a so-called missile homing device, having a wide field of acquisition, to localize the missile as soon as it leaves the launch ramp, and to determine coordinates enabling the missile to be brought back to the line of sight of the target-tracking device. The standard way to home the missile is either by remote control or by a directive beam.
2. Description of the Prior Art
Known missile homing devices are of the wide-angle radar type, or of the directive laser beam type or of the pseudo-imaging or infrared imaging type.
Pseudo-imaging or infrared imaging devices localize the missile by the infrared radiation from the jet pipe. They include an optomechanical scanning device and one or more sensors that are photosensitive in the infrared range. For example, the optomechanical device scans the image of an acquisition field having an angular width of 10.degree., in the form of a square image that is analyzed in 100.times.100 pixels.
A video signal resulting from this analysis is applied to electronic processing means in order to detect the presence of the missile and to determine its coordinates with respect to a reference point centered on the image. These coordinates express the angular deviation between the direction in which the missile is located and a line of sight common to the homing device and to the target-tracking device. Since these known homing devices analyze the entire acquisition field, which is wide, the scanning should be fast and the pass-band of the electronic processing means should therefore be wide. This diminishes the sensitivity of the device and, hence, reduces the range of the homing device, or else it calls for more complex processing and image-analyzing means to obtain a big range. Furthermore, the missile is always on the border of the field at the start of flight, hence a large part of the field that is far from the part where the missile is located is analyzed unnecessarily. This makes the homing device sensitive to the presence of the sun or of decoys